arXiv subjects

R. Kraft

Publications and source records attributed to R. Kraft.

39 records · Page 3Linked to original sources

arXiv2004

Infall of the Elliptical Galaxy NGC 1404 into the Fornax Cluster

We use three Chandra observations, totalling 134.3 ks, to constrain the dynamical motion of NGC1404 falling towards the dominant elliptical NGC1399 through the Fornax ICM. NGC1404's surface brightness profile shows a sharp edge \~8 kpc from its center in the direction of NGC 1399, characteristic of jump-like temperature and density discontinuities from ram-pressure stripping of the galaxy gas. We find the temperature of the galaxy gas inside the edge is \~2.8 times cooler (kT=0.55^{+0.01}_{-0.02} keV; abundance A = 0.73^{+0.65}_{-0.16} solar) than the cluster gas (kT,A = 1.53^{+0.10}_{-0.13} keV, 0.42^{+0.2}_{-0.13} solar). We use the shape of the surface brightness profile to fit the edge position, power law index of the density distribution inside the edge, and density discontinuity at the edge. The electron density inside the edge (3.9-4.3 x 10^{-3} cm^{-3}) depends strongly on the gas abundance; while the density of the ICM (7-8 x10^{-4} cm^{-3}) depends strongly on the assumed relative distance between NGC1404 and NGC1399. The pressure jump (1.7-2.1) across the edge and the cluster free-stream region implies a Mach number 0.83-1.03 and velocity 531-657 km/s for NGC1404 relative to the ICM. The inclination angle of the motion inferred using the relative radial velocity between NGC1404 and NGC1399 as representative of that between NGC1404 and the ICM, is uncomfortably large (>40 deg.) given the sharpness of the edge, suggesting either a non-zero impact parameter between the galaxies, or that NGC1399 is moving radially with respect to the cluster ICM.

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arXiv2004

Hot Gas Structure in the Elliptical Galaxy NGC 4472

We present X-ray spectroscopic and morphological analyses using Chandra ACIS and ROSAT observations of the giant elliptical galaxy NGC 4472 in the Virgo cluster. We discuss previously unobserved X-ray structures within the extended galactic corona. In the inner 2' of the galaxy, we find X-ray holes or cavities with radii of ~2 kpc, corresponding to the position of radio lobes. These holes were produced during a period of nuclear activity that began 1.2 x 10^7 years ago and may be ongoing. We also find an asymmetrical edge in the galaxy X-ray emission 3' (14 kpc) northeast of the core and an ~8' tail (36 kpc) extending southwest of the galaxy. These two features probably result from the interaction of NGC 4472 gas with the Virgo gas, which produces compression in the direction of NGC 4472's infall and an extended tail from ram pressure stripping. Assuming the tail is in pressure equilibrium with the surrounding gas, we compute its angle to our line of sight and estimate that its true extent exceeds 100 kpc. Finally, in addition to emission from the nucleus (first detected by Soldatenkov, Vikhlinin & Pavlinsky), we detect two small extended sources within 10'' of the nucleus of the galaxy, both of which have luminosities of ~7 x 10^38 erg/s.

astro-ph↗

arXiv2004

Reflections of AGN Outbursts in the Gaseous Atmosphere of M87

We combined deep Chandra, ROSAT HRI, and XMM-Newton observations of M87 to study the impact of AGN outbursts on its gaseous atmosphere. Many X-ray features appear to be a direct result of repetitive AGN outbursts. In particular, the X-ray cavities around the jet and counter jet are likely due to the expansion of radio plasma, while rings of enhanced emission at 14 and 17 kpc are probably shock fronts associated with outbursts that began 1-2\times10^7 years ago. The effects of these shocks are also seen in brightenings within the prominent X-ray arms. On larger scales, ~50 kpc from the nucleus, depressions in the surface brightness may be remnants of earlier outbursts. As suggested for the Perseus cluster (Fabian et al.), our analysis of the energetics of the M87 outbursts argues that shocks may be the most significant channel for AGN energy input into the cooling flow atmospheres of galaxies, groups, and clusters. For M87, the mean power driving the shock outburst, 2.4\times 10^{43} ergs/sec, is three times greater than the radiative losses from the entire ``cooling flow''. Thus, even in the absence of other energy inputs, outbursts every 3\times10^7 years are sufficient to quench the flow.

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